The chasing bit is typical of immature / low ranking males. In the presence of mature males, those that employ chasing are much less active and often do not even attempt to mate hens / pullets. Avoid use of term "rooster" as too vague to permit quality communication on these issue. Indicate a males age based on months if less that a year of age and be prepared to use the term "cockerel". Males older than a year are best referred to as "cocks" and typically have a very different approach for females that usually does not involve chasing unless meeting a female from another flock.